This invention relates generally to medical equipment and more particularly to non-invasive systems for monitoring arterial oxygen saturation, pulse rate and blood pressure.
Various anesthesia systems are commercially available for delivering anesthesia gases to the patient. Some of such prior art systems, in addition to providing means for monitoring machine functions, also include monitors for non-invasive measurements of the patient's blood pressure, oxygen saturation and pulse rate. Such monitors typically include alarm devices for providing a visual and/or audible alarm in the event that the monitored parameters deviate from predetermined limits or settings.
In some anesthesia systems non-invasive monitoring of blood pressure is accomplished by utilizing an inflatable blood pressure cuff which is wrapped about the arm of the patient. The cuff is connected via a hose with leuer lock fittings to a monitor. The monitor may comprise oscillometric means for determining the patient's systolic, diastolic and mean blood pressure (mean arterial pressure).
In some anesthesia systems non-invasive measurement of arterial hemoglobin oxygen saturation and pulse rate is accomplished through the use of a pulse oximeter monitor utilizing a clip or probe arranged to be secured to the patient's finger. The clip includes spectrophotometric infrared transmission means and sensors to provide signals from which arterial hemoglobin oxygen saturation and pulse rate are calculated by the monitor.
As will be appreciated by those skilled in the art when it is desired to take a person's blood pressure while also monitoring his/her arterial hemoglobin oxygen saturation and pulse rate utilizing monitors as described above, it is the accepted practice to place the blood pressure sensing cuff on one arm of the patient and the oxygen saturation/pulse rate monitoring probe on the finger of the hand on the other arm since the inflation of the blood pressure cuff occludes or obstructs the flow of blood through the arm. Thus, if the oxygen saturation sensing probe were disposed on the finger of the arm about which the pressure cuff was inflated the flow of blood to the finger would be impeded, whereupon the oxygen saturation/ pulse rate monitor would provide a false alarm signal indicating a deviation from the pre-established limits or set points. Such a false alarm is a nuisance since it disrupts communication among operating personnel in the vicinity of the system, while also detracting from perceived urgency of actual alarm conditions.
In some cases, such as when a patient has had surgery on one arm, it is not possible nor practical to measure blood pressure on one arm and oxygen saturation on the other. Thus, if both the pressure cuff and the oxygen saturation/pulse rate probe are to be used on one arm, the need exists for an interlock system to preclude the generation of spurious or false alarms by the pulse oximeter monitor when the cuff is in place and inflated.